Mobile wireless communication is becoming increasingly important for safety, convenience, and efficiency. One prominent mobile communication option is cellular communication. Cellular phones, for instance, can be found in cars, briefcases, purses, and even pockets. As cell phones have become smaller for improved portability, battery size and weight has become a critical barrier to further cell phone miniaturization. One technique to limit the required size and weight of batteries is to reduce the power demands placed on them. Consequently, cell phone portability (as well as standby and talk time) can be improved through power management.
In wireless communications systems, procedures for establishing communication and transmitting messages between mobile terminals and base stations are defined. For instance, when a mobile terminal wishes to transmit a message or set-up a phone call, the mobile terminal must establish communication with a proximate base station.
Referring to FIG. 1A, a cell in a mobile communications system is diagramed at 100. In cell 100, two mobile terminals are attempting to establish a connection with a base station 110. A mobile terminal 120 is xe2x80x9cattempting to secure a random access channelxe2x80x9d (ASRAC) via ASRAC120 to the base station 110, and a mobile terminal 130 is attempting to secure a random access channel via ASRAC130 to the base station 110 (i.e., xe2x80x9crandomxe2x80x9d access). The transmission ASRAC120 is received and processed prior to the transmission ASRAC130 in this example. The phrase xe2x80x9cattempting to secure a random access channelxe2x80x9d is also termed xe2x80x9cattempting to establish a connectionxe2x80x9d (e.g., with a base station) within this document.
Referring to FIG. 1B, cell 100 is illustrated where the base station 110 is busy establishing a connection with and receiving a message from the mobile terminal 120. A downlinked control channel message 140 initially includes a response code that corresponds to the mobile terminal 120 and constantly includes information indicating that the base station 110 is busy (e.g., a xe2x80x9cBxe2x80x9d). Note that for diagrammatical clarity thin arrows represent point-to-point transmissions while thick arrows represent point-to-multipoint transmissions, such as from the base station 110 to all mobiles within cell 100.
The mobile terminal 130 receives and processes the information in the downlink control channel message 140. The mobile terminal 130 must continue to monitor the downlinked control channel message 140 until the busy indication xe2x80x9cBxe2x80x9d is changed. Unfortunately, this monitoring consumes battery power in the mobile terminal 130. Note that although the mobile terminals 120 and 130 are represented as vehicles, this is primarily to represent their mobility. In fact, the mobile terminals 120 and 130 may be hand-held devices in which battery life is a critical feature to users.
Continuing now with FIG. 1C, a cell 100 is illustrated where a base station is idle and available for an attempt to establish a connection with a new mobile terminal. Once the base station 110 has completed the communication with the mobile terminal 120, the base station 110 transmits a downlink control channel message 150 with an idle indication xe2x80x9cIxe2x80x9d. The mobile terminal 130 detects the idle indication xe2x80x9cIxe2x80x9d and responds with another ASRAC130 to establish a connection with the base station 110. The mobile terminal 130 can then complete the useful process of transmitting its message.
In contrast to the useful connection establishment and message transmittal procedure diagramed in FIG. 1C, the mobile terminal 130 is achieving no useful purpose while it consumes energy in FIG. 1B. The mobile terminal 130 is monitoring the downlink control channel messages 140 to detect when the indication switches from xe2x80x9cBxe2x80x9d for busy to xe2x80x9cIxe2x80x9d for idle. This monitoring consumes power and can last for an extended amount of time when, for example, the mobile terminal 120 in FIG. 1B is transmitting a lengthy message.
In summary, mobile terminals in the prior art have heretofore been required to expend battery power while monitoring a downlinked communication from a base station when they wish to establish a connection with the base station and the multiple access channel is currently busy.
The system and method of the present invention, which belongs to the field of power management for extending the useful battery life of mobile terminals in wireless communications systems, enables mobile terminals to reduce power while waiting for a shared multiple access channel to become available. In accordance with the present invention, a base station transmits information that indicates the amount of time remaining until a current occupier of the shared multiple access channel will complete its message.
Traditionally, when a second mobile terminal wishes to transmit a message over a shared multiple access channel that is currently occupied by a first mobile terminal, the second mobile terminal constantly monitors the shared multiple access channel downlink in order to detect when the channel switches from busy to idle. This constant monitoring squanders battery power and, therefore, contributes to large battery requirements and unnecessarily reduces the standby and conversation time of the second mobile terminal.
According to the present invention, during a message transmission of the first mobile terminal, the base station transmits, in addition to a busy indication, a number of remaining units that corresponds to the number of units remaining until completion of the first mobile terminal""s message. When the second mobile terminal checks the multiple access channel downlink because it wishes to transmit its own message, the second mobile terminal will detect both an busy indication and the number of remaining units.
Consequently, the second mobile terminal can then cease monitoring the channel until the specified number of remaining units has transpired. Afterwards, the mobile terminal can again check the channel to determine whether the channel is indicated as idle. By ceasing the constant monitoring of the multiple access channel downlink, the second mobile terminal conserves power and thus extends the useful life of the battery.
An important technical advantage of the present invention is that it provides power management features for mobile terminals in wireless communications systems.
Another important technical advantage of the present invention is that it provides power management features for mobile terminals during random access procedures.
Yet another important technical advantage of the present invention is that it transmits durational indicators that inform mobile terminals of the time remaining until completion of a current message transmission procedure.
Yet another important technical advantage of the present invention is that it enables mobile terminals to conserve power while awaiting an idle random access channel by obviating any need to constantly monitor a busy/idle condition.
Yet another important technical advantage of the present invention is that it provides a system and method that can be implemented for new mobile terminals without interfering with the functioning of existing mobile terminals.
The above-described and other features of the present invention are explained in detail hereinafter with reference to the illustrative examples shown in the accompanying drawings. Those skilled in the art will appreciate that the described embodiments are provided for purposes of illustration and understanding and that numerous equivalent embodiments are contemplated herein.